Unmanned Systems Technology 026 I Tecdron TC800-FF I Propellers I USVs I AUVSI 2019 part 1 I Robby Moto UAVE I Singular Aircraft FlyOx I Teledyne SeaRaptor I Simulation & Testing I Ocean Business 2019 report

30 Closed-loop motor control The closed-loop motor control system is designed to increase the accuracy and precision of the robot’s movements, particularly when operating with a heavy load over rough ground. That makes control of the robot easier and more comfortable for the operator, Mammana says. “In practical terms, it gives a lightweight feel to piloting the robot.” Like all tracked vehicles, the TC800- FF steers by manipulating the tracks so that they move at different speeds or different directions. A gentle left turn with the vehicle moving forwards, for example, would involve slowing the track on the left side while maintaining speed or even accelerating the track on the right. Similarly, turning the tracks in opposite directions with the vehicle stationary would turn it on the spot. The motor controllers are supplied by Roboteq, which says it offers equipment that can implement a variety of control schemes. In closed-loop speed mode in brushless motors, for example, the Hall effect sensor is used to measure the motor speed, and if the speed changes because of a change in load the controller adjusts the motor’s power output to compensate. In closed-loop position modes – including position relative, count position and position tracking – the controller uses the sensor to compare the angular position of the axle with a desired position. In the position-relative mode, the motor moves from a starting position to a destination position using a controlled acceleration, velocity and deceleration. Count-position mode works in a similar way, but the motor can be commanded to go to any count position value using a controlled acceleration and velocity profile. In position-tracking mode the motor goes to the commanded position as quickly as possible. The TC800-FF can be equipped with two types of track, one optimised for range/endurance, the other for performance on rough terrain and low- traction surfaces, which Mammana likens to summer and winter tyres for a car. Each continuous rubber track is driven by its own motor via a reduction gearbox and a sprocket mounted at the front of the chassis. There are four pairs of weight-bearing wheels per track, with the front and rear pairs being larger than the two sprung pairs in between, while a single pair of wheels on each side support the top run of the track. All of these are attached to a box- section steel tube mounted on the side of the chassis. The rear wheels are bolted to this tube via slotted plates that enable operators to adjust track tension. The decision to develop the computer in-house was also driven by the desire to offer greater versatility, more reliability and the ability to respond more quickly to requests from customers. “Our computer now matches our exact requirements in terms of applications,” Mammana says. “We have direct control of it and the new developments we want to carry out software-wise. We don’t have to rely on a third party anymore.” Energy supply When it came to the energy system, Tecdron chose a bespoke solution from specialist battery supplier Neogy. It designs batteries for electric vehicles, both ground-based and airborne, and the 48 V system supplied for the TC800-FF consists of two CE-certified 25 kg lithium- ion batteries tailor made for the TC800- FF, a battery management system (BMS) and an internal comms system that enables them to interact with each other and with the UGV. “Given the extreme constraints related to the robot’s engagement during firefighting operations, it is essential that its batteries offer a very high level of safety against shocks, vibration, temperature, humidity and misuse,” says electrical engineer Richard Breuiller. The TC800-FF’s batteries feature nickel manganese cobalt lithium-ion cells connected in series and parallel. The BMS manages the status of both batteries together, and displays information on the run time and battery life remaining in percentage terms. It also protects the cells from overload and deep discharge, provides over- June/July 2019 | Unmanned Systems Technology The weight-bearing wheels and track tensioning system are attached to a box- section steel tube mounted on the side of the chassis (Courtesy of Tecdron)